Adoption scorecard data released by the Department for Education show county youngsters wait 689 days to be placed, on average.

The comparable figure for England over the same period (2009-2012) was 636 days.

Unison has called Essex County Council’s figures “extremely disappointing”, while an adoption charity urged authorities to “re-double” their efforts.

But Essex County Council said its record on adoptions was strong and highlighted the importance of finding the right family for each child.

John Simmonds, director of policy research at the British Association of Adoption and Fostering, said: “At the heart of the scorecards are children in the most vulnerable of circumstances. Fifty years of research has established that children need a secure, stable and loving family as quickly and as early in life as possible.

“There are many hurdles to ensuring that this happens where adoption is the plan and this has become the focus of considerable recent activity both in local authorities and the courts to address this.

“There is clearly some way to go and the publication of new scorecard data must re-double our efforts to overcome these hurdles.

“At the end of the day it is the child’s needs that matters.”

Nalin Cooke, Unison spokesman at the county council, said: “It’s extremely disappointing to hear that kind of data because the council has an obligation to try and make this transition as quickly as possible - that is what is best for children.

“My experience is hundreds and hundreds have lost their jobs and this impacts on services. I know staff morale is low and people are working quite long hours and this will have an impact on outcomes.”

Ray Gooding, cabinet member with responsibility for children’s services at the council, said: “Essex has a strong commitment and track record on adoption. Ofsted earlier this year rated the service as good with outstanding features.

“We are proud to get it right for children first time when we move them to an adoptive family. 20% of adoptions nationwide are reported to disrupt whilst none of the 46 children placed by Essex since April this year have disrupted.

“The service has already identified that it wants to improve its adoption timescales and it is already doing so.”